Growth percentile calculator for children and teenagers

Q: Which percentile is normal?

The range from the 3rd to the 97th percentile is considered normal. Values between the 3rd and 10th or 90th and 97th percentile are borderline and worth monitoring.

Q: Polish or WHO charts — which should I use?

In Poland the WHO standards are recommended up to 3 years and the Polish OLA and OLAF references from 3 to 18 years. WHO charts for older children are useful for international comparisons.

Q: Can I enter the age in days?

Yes. In “enter age” mode give years, months and days in any combination, e.g. only days for a newborn. You can also enter the date of birth and date of measurement.

Enter the child’s age or date of birth, sex and measurements. We calculate weight, height, BMI, weight-for-length and head circumference percentiles, plot them on the chart and keep a measurement history.

How to read percentiles

A percentile shows what share of healthy children of the same age and sex have a lower value. The 25th height percentile means 25% are shorter and 75% taller.

Percentile	Meaning
< 3	below the normal range — needs assessment
3–10	borderline — monitor
10–90	normal
90–97	borderline — monitor
> 97	above the normal range — needs assessment

The growth trajectory matters more than a single measurement: a child who grows steadily along one centile channel is growing harmoniously, even if it is a low channel. Crossing two centile lines up or down is a warning sign.

BMI in children

In children BMI is assessed for age and sex. In the Polish charts (3–18 years) the overweight, obesity and underweight limits are the centiles that reach a BMI of 25, 30 and 18.5 kg/m² at age 18 (IOTF-like method):

	Boys	Girls
Underweight	< 8.4 c	< 15.8 c
Overweight	≥ 82.9 c	≥ 90.5 c
Obesity	≥ 97.5 c	≥ 98.6 c

Under 5 years (WHO standards) BMI and weight-for-length are assessed in standard deviations: above +1 SD — risk of overweight, above +2 SD — overweight, above +3 SD — obesity, below −2 SD — wasting. In the WHO 2007 references (5–19 years) overweight is above +1 SD, obesity above +2 SD and thinness below −2 SD.

Charts and method

Polish charts (as recommended by the Children’s Memorial Health Institute, Warsaw): WHO standards up to 3 years, OLA study 3–6 years, OLAF study 7–18 years; between 6 and 7 years we interpolate between OLA and OLAF. WHO charts: growth standards 0–5 years and the WHO 2007 reference 5–19 years (weight-for-age only up to 10 years). Head circumference and weight-for-length/height use WHO up to 5 years.

Percentiles use Cole’s LMS method: z = ((X/M)^L − 1) ÷ (L × S); the percentile is the normal cumulative distribution of z. For WHO weight-based indicators beyond ±3 SD we apply the WHO-recommended restriction.

Frequently asked questions

Which percentile is normal?

The range from the 3rd to the 97th percentile is considered normal. Values between the 3rd and 10th or 90th and 97th percentile are borderline and worth monitoring.

Polish or WHO charts — which should I use?

In Poland the WHO standards are recommended up to 3 years and the Polish OLA and OLAF references from 3 to 18 years. WHO charts for older children are useful for international comparisons.

Can I enter the age in days?

Yes. In “enter age” mode give years, months and days in any combination, e.g. only days for a newborn. You can also enter the date of birth and date of measurement.

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This calculator is for education and does not replace a doctor’s assessment. Always interpret the result together with the history and examination.

Growth percentile calculator for children and teenagers

Measurements

Growth charts

Measurement history